1. Field of Invention
The present invention refers to a folding lifting device to be used in the construction of large metal containers, and a removable fitting applicable to such device. That is, to a collapsible hoisting device for use in the construction of large metal containers, and removable accessory applicable thereto. The characteristics of the present invention facilitate the construction procedures reducing construction time and costs.
2. Description of Related Art
It is known that in order to perform the assembly of various structures it is necessary to have a system that is able to lift part or the whole of the structure. In particular, for the construction of large metal tanks or containers applying the method which consists of constructing first a ring and the roof attached to it, and subsequently lifting the structure and attaching new rings, always working close to the floor, the use of devices able to lift the growing structure in a safe and effective way without disturbing the assembly process becomes critical.
Currently, in the present state of the art some of the disclosed lifting devices are limited in general to several models of hydraulic or mechanic jacks, which show drawbacks in their use that the present device has solved.
Among said jacks, those described in the U.S. Pat. No. 7,500,592 B1 (Yaksic) dated Mar. 10, 2009 describing the use of non-folding hydraulic jacks can be mentioned.
Spanish Utility model application ES 1045850 U (Carinox) dated Apr. 4, 2000 and Spanish patent ES 2 208042 B1 (Carinox) dated Feb. 28, 2005 disclose hydraulic jacks especially aimed at assembling and disassembling vertical tanks, which among other differences with the present invention, do not feature removable support fittings.
Regarding jacks layout, said U.S. Pat. No. 7,500,592 B1 (Yksic) discloses the use of three independent but coordinated hydraulic systems. Thus, the number of hydraulic jacks used must be a multiple of 3. Spanish patent ES 2 211 268 B1 (Cariñox) dated Mar. 8, 2005 describes the operating station for hydraulic systems of this type, whereas Spanish patent ES 2 213 436 (Cariñox) dated Jun. 29, 2005 shows a hydraulic lifting system for assembling and disassembling vertical tanks, where the hydraulic jacks are divided into groups of independent operation for the optimum control of structure verticality.
On the one hand, the lifting device must be able to grasp or hold the structure safely. To this purpose, the technologies known usually weld accessory supports in the structure as a kind of handles, that the jack uses as a lock or bearing point to support the structure during the lifting operations. On completion of the work, said supports must be removed, which requires considerable manpower and affects the work finishing.
On the other hand, the presence of a jack prevents operators from working freely. This detail is of vital importance in the construction of metal tanks, since it is crucial to ensure the welding quality of the layers constituting the walls of the container to guarantee the structure strength of the whole. In this case, the device supporting the structure while a new ring is assembled prevents automatic welding machines from being used.
Additionally, the device itself must be firmly placed, which in general, implies welding its base to the bottom of the tank with the subsequent expense of necessary resources to unweld it once the job is complete.
The device of the present invention solves all these problems, reducing the temporary welding necessary for assembly to the minimum and allowing its folding so as to allow improvement on the construction conditions of containers.